In paint shops such as automobile repaint shops, production is limited by the time required for the paint to dry. Spray booths are frequently used both to confine paint overspray and evaporated solvents and to reduce drying time. As used herein, the term "paint spray booth" is intended to cover both spray booths in which workpieces are painted and dried and booths in which a painted workpiece is dried or cured. In the past, paint spray booths often used an array of infrared lamps for applying heat to the painted automobile or other painted workpiece for accelerating drying. The automobile may be heated, for example, to about 130.degree. F. (about 55.degree. C.) during drying. In a downdraft automobile paint spray booth, the automobile is positioned over an open floor grate. Booth air and any entrained paint overspray and solvents are drawn downwardly over and around the vehicle during spraying and drying and exhausted through the floor grate. A vehicle is typically subjected to an air flow on the order of 20 feet per minute (6.1 meters per minute) over horizontal surfaces. In a cross draft booth wherein the air flows in a horizontal direction through the booth, typical surface air flow velocities are about 75 to 100 feet per minute (22.9 to 30.5 meters per minute). When the automobile surfaces are heated to about 130.degree. F. (about 55.degree. C.) at these flow velocities, it may take up to 60 minutes for the entire vehicle to dry sufficiently to permit removal from the spray booth. Until the automobile is dry, it must be kept in the spray booth to prevent damage to the soft paint. It should be appreciated that the total drying time is limited by the slowest drying surface areas which may not be subjected to significant air flow.
In order to increase the number of automobiles that can be painted in a given time, attempts have been made to decrease the drying time that each automobile must spend in the spray booth. Most commonly, infrared heat from permanently installed or portable heat lamps is used. Since the heaters require careful positioning to be effective, permanently installed lamps may not be as effective as portable lamps. Heaters must have electrical interlocks if used inside the booth or they must be rolled out of the booth during spraying to reduce the risk if igniting any flammable solvents. Attempts also have been made to increase the surface air flow over the vehicle. Nozzles have been mounted on rigidly plumbed headers along the booth ceiling. Compressed air is delivered from an external source to the nozzles for increasing the air flow over painted surfaces. However, problems have been encountered with these systems. The fixed nozzles did not offer flexibility with different vehicles. Further, there was an increased risk of contaminating the wet paint with, for example, dust and oil in the compressed air. Typically, the compressed air was obtained from a conventional shop compressor and compressed air distribution systems. However, the air nozzles required a very high air flow rate in order to be effective, thereby increasing the operating costs and consuming compressed air needed for operating spray guns and other shop tools.